Problem: Simplify to lowest terms. $\dfrac{25}{30}$
What is the greatest common factor (GCD) of 25 and 30? $25 = 5\cdot5$ $30 = 2\cdot3\cdot5$ $\mbox{GCD}(25, 30) = 5$ $\dfrac{25}{30} = \dfrac{5 \cdot 5}{ 6\cdot 5}$ $\hphantom{\dfrac{25}{30}} = \dfrac{5}{6} \cdot \dfrac{5}{5}$ $\hphantom{\dfrac{25}{30}} = \dfrac{5}{6} \cdot 1$ $\hphantom{\dfrac{25}{30}} = \dfrac{5}{6}$